Dynamic RAM (DRAM)

DRAM must be continually refreshed in order to maintain the data. This is done by
placing the memory on a refresh circuit that rewrites the data several hundred times

per second.

DRAM is used for most system memory because it is cheap and small. All DRAMs
are made up of memory cells which are composed of one capacitor and one

transistor.

Electrically erasable programmable ROM (EEPROM)

EEPROM is a type of non-volatile memory used in computers and other electronic
devices to store small amounts of data that must be saved when power is removed, for
example, calibration tables or device configuration.

Modern EEPROMs allow multi-byte page read/write operations as well as data

read/write lock. Limitation of EEPROM is less number of data program cycles

FLASH

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Flash memory is non-volatile advanced type of EEPROM mostly used in
Microcontrollers and other electronics device to store the firmware. There are two main

types of flash memory

‎NAND Flash—NAND type flash memory may be written and read in blocks (or pages).‏ ۔

‎The NAND type is primarily used in main memory, memory cards, USB flash drives,
solid-state drives, and similar products, for general storage and transfer of data.

‎NOR Flash — NOR type flash allows a single machine word (byte) to be written to an
erased location or read independently. NOR flash memory is also often used to store
configuration data in numerous digital products, a task previously made possible by
EEPROM

‎The main feature of flash memory is that when packaged in a “memory card,” it is
extremely durable, being able to withstand intense pressure, extremes of temperature,
and even immersion in water.

‎Flash memory has better kinetic shock resistance than hard disks.

‎CACHE MEMORY

‎Cache memory, also called CPU memory used to reduce the average time to access data
from the main memory. The cache is a smaller, faster memory which stores copies of
the data from frequently used main memory locations.

‎It is in-built in CPU.